(urth) Cumaean???

Kerry Benton k.benton at gmail.com
Sat Dec 15 09:25:03 PST 2007


> Maybe the moon is getting closer because of alterations
> on the gravitational force at the solar system level due to the black hole
> in the center of the Sun? Seems more reasonable.

This is an interesting possibility, but I've always simply assumed
(perhaps belying simplicity of intellect on my part) that the moon is
not actually closer, but merely has a larger apparent size.  I no
longer recall if the actual relative size was described.  Still, a
body with an atmosphere is bound to be, for lack of a better term,
fuzzy, since the scattering of light through the atmosphere will be
visible.  This might increase the apparent (e.g. "bright") diameter of
the body by a few percent.  Scattering in Earth's atmosphere produces
that brilliant blue halo, if I recall my physics classes.

Perhaps I'm forgetting clear evidence presented in the work that the
moon actually is closer, to which I'll certainly defer.

>  I dont know either, but it seems to me that that limit would be met before
> geting so close that the atmospheres would touch (as is told in the Book of
> the Short Sun).

It's dependent upon the densities and radii of the bodies in question,
but, yes, the Roche limit is orders of magnitude larger for a
planet/moon system.  I see in the thread that Wikipedia says Roche is
about 9500 km for Earth/Moon...  the earth's atmosphere, even being
generous, is about 40 km.  Collisions (and atmospheric interaction may
as well be on these scales) requires the satellite body to be very
small or else very dense.

-k



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